Fire Protection for Airport Ground Support Equipment

Introduction

At airports in these post-pandemic days, business is booming and only expected to get busier. According to the International Air Transport Association (IATA), this year, the overall number of air passengers is projected to exceed pre-COVID-19 levels, reaching an estimated 103% of the total seen in 2019.

The Airports Council International (ACI) World also predicts that global passenger traffic will fully recover in 2024, reaching approximately 9.4 billion passengers (again, surpassing the numbers from 2019). This recovery is attributed to several factors, including the easing of travel restrictions, the return of consumer confidence in air travel, and recovering economic conditions which have spawned renewed interest in global mobility.

This robust recovery has also caused an increase in worldwide aircraft sales. While the aircraft themselves are the undisputed stars of the show, they are totally dependent on the airport ground support equipment (GSE) that service them. The increased number of aircraft in service and the resurgence of air travel means that more and more airport ground support equipment will also be in service.

All of this equipment is powered by diesel, gasoline, propane/natural gas, or electric/hybrid drivers, each of which carries the risk of catching fire. While much attention is paid to fire protection on aircraft or the airport proper, fire protection measures on valuable pieces of equipment are often overlooked. And that is a mistake.

The Fire Risk

Any fire on airport premises can be costly and have tragic consequences. Since most airport ground support equipment operates in close proximity to the aircraft it is servicing, there is always a chance that a fire on the ground support equipment could spread to a fully occupied aircraft. Anyone who has experienced air travel understands that egress from aircraft is almost always a cumbersome affair. If the aircraft is on fire, it can cost people their lives.

Airport ground support equipment also operates in, around, and even under airports increasingly at full capacity around the clock. Again, a fire originating from airport ground support that spreads to the airport itself has great potential to end badly.

Aside from the life safety risk, a fire that impacts an airport to any real degree will wreak havoc on air travel. Flight delays are all but guaranteed, and it may take significant time for the airport to recover and return to normal operations. This is very costly to the airport and/or the airlines in terms of lost revenue.

There is also the cost of the equipment that may be involved in a fire incident. Commercial aircraft start at about $55 million and go up from there. The ground support equipment is not cheap either, with most of it carrying hefty six-figure price tags.

The exposure from a fire that starts on airport ground support equipment is great and should not be ignored. But since they operate in a behind-the-scenes capacity, they are not always on the minds of those charged with fire safety of airport operations.

The typical fire protection arrangement on airport ground support equipment is to mount a portable fire extinguisher on the equipment. This is a good first step, but its effectiveness is dependent upon someone being present to use it, and someone who is properly trained. It also depends on the size of the fire being within the capacity of the fire extinguisher’s capability.

As we will describe, the best and safest approach is to have an automatic fire suppression system onboard each piece of airport ground support equipment that possesses a potential fire risk. This removes the human variable, as the automatic fire suppression system is always on duty and does not have to perform complex decision making during an emergency.

A properly designed onboard fire suppression system is also purpose built for the fire scenario it is expected to handle. It has sufficient capacity for the expected fire and is mounted in such a way that it directs the agent to the fire area. It is also designed for the expected class of fire that will be encountered—i.e., Class A, B, and/or C.

In this article, we will discuss the various types of airport ground support equipment, describe the fire risk for each, and provide guidance on fire protection solutions for each.

The good news for airport fire safety personnel is that Stat-X fire protection solutions for each type of equipment are available today. Read on to learn more.

Types of Airport Ground Support Equipment and Their Fire Risk

Aircraft Pushback Tugs
One of the more common airport ground support equipment pieces is the aircraft pushback tug. These vehicles are used to push aircraft away from the gate to a position where they can start their engines and proceed to the runway under their own power. They are also used to move aircraft around for maintenance.

There are a few different types of pushback tugs in service that may be encountered, and tugs can be powered by a variety of fuel sources. Because they are constantly operating very close to the aircraft, a fire that starts on a pushback tug has the distinct possibility of spreading to the aircraft.

First, let’s examine how pushback tugs are powered. This is logical because a fire on a tug will most likely originate from its power source. Around the world, pushback tugs can be found powered as follows:

• Diesel-powered: Traditional pushback tugs are often powered by diesel engines. These tugs are robust and powerful, making them suitable for handling a wide range of aircraft sizes, from small commercial jets to large wide-body aircraft.
• Electric-powered: Electric pushback tugs are becoming more popular as a cleaner alternative. These tugs use lithium-ion battery packs to operate and are known for being quieter and producing zero emissions at the point of use.
• Hybrid: Some pushback tugs combine diesel and electric power, which can help reduce emissions while still providing the power needed for heavier aircraft. Hybrid pushback tugs use the electric motor for general maneuvering and the diesel engine for additional power when necessary.
• Gasoline-powered: Less common than diesel, some smaller pushback tugs use gasoline engines. These are typically used for smaller/lighter aircraft.
• Propane/natural gas-powered: Another alternative for smaller pushback tugs is propane, which emits fewer pollutants than diesel or gasoline. Propane pushback tugs are used in environments where lower emissions are a priority but full electric power is not feasible.

Aside from the variety of power sources, there are basically two different types of pushback tugs in service at airports today:

• Conventional: This pushback tug uses a tow bar to connect to the nose gear of the aircraft. The tug driver steers and operates the tug while the aircraft’s landing gear freely pivots. Conventional pushback tugs are versatile and can handle a wide range of aircraft sizes, from small private planes to large commercial jets. Conventional pushback tugs can be powered by any of the sources listed above.
• Towbarless (TBL): TBL pushback tugs do not use a tow bar. Instead, they lift the nose wheel of the aircraft off the ground and cradle it, allowing the tug to maneuver the aircraft. This design reduces the setup time and can be more efficient, especially for quick turnarounds. TBL pushback tugs are suitable for a variety of aircraft sizes and types and are typically powered by diesel, electricity, or a hybrid arrangement. The design of a TBL tug does, however, place the hydrocarbon engine or electric motor(s) / lithium-ion battery pack directly under the aircraft.

The primary fire risk on a pushback tug is its hydrocarbon engine or electric motor(s) along with the lithium-ion battery pack. A hydrocarbon fuel leak that contacts a hot surface will easily produce a fire. Electric motors can overheat, short circuit, or arc, any of which can produce a fire. Additionally, with electric vehicles (EVs), the onboard lithium-ion battery pack is always at risk of experiencing a battery failure leading to a thermal runaway which results in a fire or explosion.

The fire protection solution on pushback tugs is simple. Tugs with a hydrocarbon engine require an automatic fire suppression system in the engine compartment. Pushback tugs using electric motors require a fire suppression system at each motor and also for the lithium-ion battery back. TBL tugs in particular should be fully protected; as they operate under the aircraft, any fire while the tug is connected to an aircraft has a high probability of spreading to the aircraft.

Baggage Tugs and Belt Loaders

Close relatives to the pushback tug are the baggage tug and belt loader. Like the pushback tugs, this equipment has the same availability of power sources and usually operates close to the aircraft. Consequently, their fire risk and fire protection solution are the same as stated for the pushback tugs.

Ground Power Units (GPUs) and Air Start Units (ASUs)

GPUs provide power to aircraft when their engines are not running, allowing onboard systems and cabin lighting to function without draining the aircraft’s batteries. For large commercial aircraft, GPUs supply 115 Volt 400 Hz Alternating Current (AC) to the plane. There are primarily two types of GPUs used at airports:

Mobile GPUs: These are portable units that can be towed to an aircraft. They may be powered by diesel engines or battery-operated.
Fixed GPUs: Installed at airport gates, these units are connected directly to the airport’s power supply and provide a constant source of electricity to parked aircraft.

ASUs supply the necessary air pressure to start the engines of an aircraft when it is not possible to start them using the aircraft’s own power. Like the GPUs, they also exist in two formats:

Mobile ASUs: These are more common and provide flexibility in operations. Mobile ASUs are mounted on trucks or trailers and can be easily moved around the airport to wherever they are needed. Mobile ASUs are equipped with their own power source which allows them to operate independently of airport infrastructure.
Fixed ASUs: Some larger airports may use fixed ASUs, which are stationary installations connected to an airport’s central power supply. These units are typically installed at specific gates and are used to provide air start capability directly from the gate position without the need to deploy mobile units.

The primary fire protection risk in terms of airport ground support equipment lies with mobile GPUs and ASUs since they are towed to the aircraft and are powered by various means that can present a potential fire source. Much like the pushback tug, mobile GPUs/ASUs are powered by gasoline, diesel, battery, and hybrid drivers.

The hydrocarbon motors can easily experience a fire in the engine compartment, while the battery and hybrid-driven units are at risk for a fire in the electric motors/generators and lithium-ion battery pack.

As with the pushback tugs, the fire protection solution is again simple. Units with a hydrocarbon engine require an automatic fire suppression system in the engine compartment. Units employing electric motors or generators require a fire suppression system at each motor or generator, as well as for the lithium-ion battery back.

Miscellaneous Airport Ground Support Equipment

Aside from the equipment we have already discussed, there is a veritable fleet of other vehicles that may be present on the tarmac to service aircraft. All of these vehicles, as set out below, also present a fire protection risk that should be addressed.

Deicing vehicles: These are equipped to spray deicing fluid on aircraft surfaces to remove ice and snow, ensuring safe operations in winter weather.

Fuel trucks: Also known as “refuelers,” these trucks supply fuel to aircraft. They can either be hydrant trucks (which connect to a central airport fuel supply) or tanker trucks (which carry their own supply of fuel).

Catering vehicles: These vehicles are equipped to reach the height of aircraft doors for loading and unloading in-flight meals and beverages.

Passenger buses: In airports where the terminal is a significant distance from the aircraft, passenger buses transport travelers to and from the aircraft.

Stair cars: Also known as “airstairs,” these vehicles provide stairs that allow passengers to board and disembark the aircraft, particularly when a jetway or aerobridge is not available.

Lavatory service vehicles: These vehicles are used to empty onboard lavatories and replenish them with fresh water.

Maintenance vehicles: Various specialized vehicles are used for aircraft maintenance, including lifts for high-up work and trucks equipped with tools and parts.

As with all airport ground support vehicles, these vehicles’ fire risk primarily lies with their source of power. And like all the others, these can be driven by gasoline, diesel, propane/natural gas, hybrid, or electric power.

Again, the fire risk lies in the engine compartment of the hydrocarbon-driven vehicles and the electric motors and battery packs of the electric/hybrid vehicles. Each of these areas requires an automatic fire suppression system to extinguish a fire.

The Stat-X^® Solution

Protecting this vast array of airport ground support equipment can be a daunting task. There are so many different types of vehicles and equipment, and they can be powered by varied types of drivers.

Fortunately for airport safety personnel, a single solution exists which can easily provide effective fire suppression for all types of airport ground support equipment.

Stat-X is a condensed aerosol fire suppression agent based on a proprietary potassium-based compound. Upon initiation, the aerosol cloud fills the fire area, interrupting the fire’s chemical chain reaction, and causing rapid extinguishment. Stat-X has been proven effective at extinguishing a variety of hydrocarbon fires and Stat-X systems can mitigate the risk of thermal runaway propagation. Stat-X can also fully extinguish Class A surface fires.

Stat-X is supplied in individual standalone units of robust construction and has no piping requirements. This means they are within their element mounted in harsh environments of engine compartments and around electric motors and battery packs. The units can be easily and quickly retrofitted to existing equipment.

Also of critical importance and benefit, standalone Stat-X units are thermally activated. When the surrounding temperature reaches a preset temperature, the unit activates to extinguish the fire. There is also an option to manually activate the unit. The units are supplied in various sizes to fit the particular risk.

Using a single fire protection solution such as Stat-X provides many advantages versus using several different systems for the varying scenarios. These include:

Simplicity in installation, maintenance and spare parts: A single type of system such as Stat-X can be easier to install and maintain because it involves uniform components and procedures.

Cost-effectiveness: Implementing and maintaining the Stat-X system across all airport ground support equipment will cost less than having multiple systems.

Consistency in operation: Using Stat-X across the board ensures that the operation and response to fire are consistent throughout the protected area.

In addition to the points above, fire-protection standardization with Stat-X for all airport ground support equipment just makes good sense—the system works for all of the potential risks described herein.

Moreover, and of equal import, Stat-X is environmentally safe. This is (and/or should be) a chief consideration as many fire suppression agents are experiencing problems because they have been found to be harmful to humans and/or the environment. With Stat-X, users can be assured of:

• Zero global warming potential
• Zero ozone depletion potential
• Zero atmospheric life

Stat-X is safe to use around personnel. After discharge, minimal cleanup is required.

Additionally, Stat-X users enjoy that the units are virtually maintenance free and there are no complicated testing requirements. This is a big plus as airport ground support equipment is almost constantly in motion, so there is no costly downtime for maintenance and/or testing.
. . .
With the fire safety focus at airports being on the aircraft and the terminal buildings, it is easy to overlook the ground support vehicles that make sure air travel is on time and efficient. But this equipment plays an important role and often operates in close proximity to occupied aircraft. A fire in any of this equipment can have devastating and long-lasting consequences. With Stat-X, airport safety officials can be assured of providing the highest degree of fire protection in a compact unit that is effective, safe, and easy to use.